Over the years, various techniques and devices have been developed to help a person accurately aim a firearm, such as a rifle or target pistol. One common approach is to mount on the firearm's barrel a sight or scope, through which the person views the intended target in association with a reticle, often with a degree of magnification. Although existing firearm sights of this type have been generally adequate for their intended purposes, they have not been satisfactory in all respects.
For example, existing sights typically are passive optical devices with mechanical adjustments. For example, they have fixed reticles with mechanical reticle adjustments, and/or mechanical adjustments to vary the magnification or zoom factor. Over time, these mechanical adjustments are subject to change, for example due to factors such as vibration, shock and wear.
A further consideration is that, in existing firearm sights, a user basically observes the relative positions of the reticle and target while aiming the firearm. When the target is relatively small, it can be difficult for the user to assess how precisely he or she is holding the reticle on the target. For example, one user may not be able to hold the firearm quite as steady as another user, resulting in differences in accuracy. However, in each case, the aiming errors can be so small that it is difficult for either user to perceive these errors by simply observing the relative positions of the reticle and target.
Yet another consideration is that the ability to accurately place a bullet in a target is a function of both mechanical factors and a human factor. The mechanical factors include bullet ballistics, bullet dispersion characteristics, and the degree of alignment between the sight and the firearm bore. These characteristics are largely repeatable, and it is thus possible to compensate for them. In contrast, the human factor is not repeatable or predictable, and thus it is difficult to assess this factor or compensate for it. The human factor includes the ability of a shooter to accurately hold the reticle of the sight on a target. Consequently, it is desirable to be able to record an image showing the relative positions of the reticle and target, as viewed by the shooter, at a point in time when the shooter pulled the trigger, and before the firearm experiences the recoil caused by combustion of the gunpowder or other propellant within the cartridge. This can help the user to assess the extent to which it was the human factor rather than mechanical factors which contributed to a shooting error.
Some pre-existing sights have included the capability to record an image showing the reticle and target, but do so in response to detection of the large recoil or acoustic shock produced by the combustion within the cartridge. Detection of this recoil or shock necessarily occurs after the point in time at which the image of interest would need to be recorded. Consequently, these pre-existing devices must buffer a number of images, respond to the detection of combustion by estimating an earlier point in time at which the trigger was probably pulled, and then identify and save one of the buffered images which corresponds to that estimated point in time. Due to a variety of factors such as variation in bullet caliber, this attempt to predict the time at which the trigger was pulled is inherently imprecise, and often results in the saving of an image which is not particularly useful because it represents a point in time too far before or too far after the actual trigger pull. Moreover, the need to buffer a large number of images makes it necessary to dedicate a relatively large amount of memory to this function, which is undesirable.
Still another consideration is the need to align the reticle to the bore of the firearm on which the sight is mounted. A traditional approach is take the firearm to a target range, fire a number of bullets at a target, observe the error in the resulting bullet pattern, mechanically adjust the windage (azimuth) and elevation (pitch) of the reticle, fire a number of additional bullets at a new target, observe the error in the resulting bullet pattern in the new target, mechanically adjust the windage and elevation of the reticle again, and so on. This process is very time consuming, and is also relatively expensive, due to the cost of targets, bullets, transportation to the target range, fees for use of the target range, and so forth.